1. Field of the Invention
This invention relates to automatic flue dampers for use in household and industrial applications and more particularly to a flue damper for association with a combustion apparatus, which damper is biased open during combustion periods and is equipped with electrical circuitry for substantially closing the damper following combustion periods so as to confine the heated atmosphere resulting from combustion.
2. Prior Art
Various flue dampers are known in the prior art. An example appears in U.S. Pat. No. 3,580,238, which discloses an automatic damper arrangement normally spring-biased to a closed position and solenoid-operated to an open position. For many applications, such a damper arrangement presents hazards which may result, for example, from a defective gas valve which permits gas to escape into the combustion chamber at a time when the furnace vent stack remains normally closed, thus flooding the household or other building with dangerous fumes.
U.S. Pat. No. 3,934,796 is of more recent vintage but continues the disadvantage of the preceding patent by employing a damper which is normally biased closed. U.S. Pat. No. 2,937,697 illustrates a prior art damper mechanism which closes combustion chamber outlets after combustion is shut off.
It should be noted that the practice in many parts of the United States has been to construct furnaces and the like without dampers, thus eliminating any need for a damper control mechanism at the expense of substantial losses of heated air through the open vent stack following periods of combustion.
An object of the present invention is to provide an improved automatic damper of the type normally closing a vent stack during times when combustion does not occur and equipped with safety features appropriate for a vent stack which is normally maintained closed.